強い安定密度成層下にある減衰乱流の構造(成層(1),一般講演)

概要

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The characteristics of decaying homogeneous turbulence under strong density stratification have been studied by using direct numerical simulations. By assuming the low-Prandlt-number fluids, e.g. the liquid sodium and gallium, internal gravity waves are markedly attenuated due to the large thermal conductivity, and shortly, turbulence becomes the two-component state, where vertical energy, coupled with potential energy, significantly decays, and becomes negligible as is observed in the experiment (Praud et al., J. Fluid Mech. 522, 2005, 1-33). In the horizontal plane, there appear large-scale vortices with the vertical vorticity, and those with a same sign of the vorticity increase their horizontal length scale by merging with each other. In the vertical plane, highly sheared regions represented by the horizontal vorticity also tend to horizontally increase their length scale and become layered structure by combined effects of the vortex coalescence and energy cascade into the higher vertical wavenumbers.
日本流体力学会の論文
2008-09-04